This invention relates to an apparatus and method for testing cans, and more particularly to an apparatus and method for testing a can seam to determine the quality of the seam in the can.
Since Napoleon's army first used canned foods in the early eighteen hundreds, it is clear that cans are an important part of transporting food throughout the world. Because of their importance to the distribution of food, cans are subject to very stringent restrictions and quality control standards. If a can is defective, the food therein can spoil and lose its nutritional usefulness at best. On the other hand, at the worst, if the can is defective, great illness and even death can result to the consumer of the food.
It is, therefore, highly desirable to take all reasonable steps to protect the integrity of the can and the food therein. This is especially true of a can with a seam. The seam must be perfect, in order to avoid problems with the food contained therein.
If there is a defect in the can seam causing an imperfect seam, such an imperfect seam must be detectable. An imperfect seam deviates from a normal can by only a very small amount. This defect can amount to less than a millimeter. Therefore, detection is usually impossible by visual means, because the defect is so minimal that it cannot be detected quickly and accurately by visual means. Yet such a minimal defect can be extremely dangerous and greatly compromise the integrity of the food contained in the can.
Visual detection causes a number of other problems. The visual examination slows production and is only as reliable as the person involved. Accordingly, it is desired to combine the visual means with other means of detecting improper can seams.
If the integrity of the seam for the can is maintained, great problems are avoided. If the seam may be examined and found proper efficiently, the stringent quality control and product purity required for food products can be met. At the same time, speed of production can be maintained.
It is especially desirable if the container can be tested in the normal course of processing without difficulty. It becomes clear that such testing is desirable in order to provide that protection, while at the same time minimizing interference with production.
It is difficult to test both ends of a can at the same time automatically. All cans are not perfect right angle cylinders. Even a slight deviation from this right angle cylinder forbids this dual testing because of a lack of flexibility in the positioning of the testing system. The measurements of a defective can are so small, that even a slight variation in the can prevent successful testing of both can ends. Thus, where both ends of a can are desired to be tested, a problem can result.
High speed production is a basic factor in obtaining the desired goals for food production in this day and age. If the inspection testing process and apparatus is incorporated into the normal flow of production, great advantages can be achieved.